In many warmer areas of the world, it is not unusual for boat owners to leave their boats in the water throughout the entire year. This is particularly true in coastal areas. In some cases, such boats are left in the water for years at a time.
A major problem faced by the owners of such boats is the growth of marine organisms (and in particular various plant species) on the outer surfaces of the boat. Submerged surfaces are particularly susceptible to such "fouling". The growth of marine organisms on boat hulls and submerged equipment is highly undesirable, since this fouling causes premature wear of the boats and such equipment, and affects engine and boat performance.
While such fouling is a problem for most boaters, this problem is particularly acute for owners of larger, ocean-going vessels which have inboard/outboard engine units, which are more commonly referred to by boaters as "stern drive units". Such units cannot be tilted up out of the water when not in use, as can smaller outboard engines, and remain submerged unless the boat is removed entirely from the water.
One method which has in the past been used to prohibit this growth of marine organisms on boats is the painting of boat hulls with so-called "anti-fouling paint". Such paints contain various metals such as zinc and work by galvanic action to prevent organism growth. These paints are effective to a certain degree on boat hulls. However, because of their electrolytic action, these paints are not suitable for use on metal surfaces such as those in marine engines.
Various protective engine covers have also been suggested to overcome this problem of marine growth on engines. For example, U.S. Pat. No. 5,315,949, which issued on May 31, 1994 to W. Bradley, discloses a protective cover comprising a large U-shaped frame, which together with a drawstring forms the mouth of a bag for removable installation over a boat motor. U.S. Pat. No. 3,587,508, which issued on Jun. 28, 1971 to J. Pearce, discloses a similar protective flexible bag. U.S. Pat. No. 4,998,496, which issued to H. Shaw on Mar. 12, 1991, discloses a more complicated engine shroud.
All of these prior art suggestions have significant drawbacks which render them unsuitable, or at least impractical, for use on boats with stern drive units. For example, Bradley's device cannot be used with modern stern drive units, which have a much different configuration than the "outcropping" shown in FIG. 1 of the patent. FIG. 1 of the Shaw patent shows the actual configuration of such engines much more accurately. Because of the size of such engines, Bradley's bag cannot be easily manipulated to cover a standard stern drive unit.
Furthermore, Bradley's cover, and that suggested by Pearce have the significant problem that they each lack a frame, beyond their rigid mouth portions, to keep the remainder of the bag portion open to receive the engine when the cover is placed in the water. They are "floppy" when in water, and easily catch and snag on various engine components, making them difficult to install. Often, such snagging causes such bags to tear, rendering them useless.
Another significant drawback of the Bradley cover is that the bag is difficult to open once it has been closed, since the drawstring, which is tightened by pulling a chord through the U-shaped frame, must somehow be pushed back through the frame to loosen the mouth of the bag for removal from the engine. A significantly expensive specialized sheathed cable is required for the mouth of the bag to open and close easily.
Pearce and Shaw both disclose cover units which are more concerned with engine flushing than with the inhibition of marine growth. In both devices there are complicated attachment mechanisms which seal off the interior of the units from the sea water, allowing the interiors to be flushed with fresh water. Such devices, while useful for the preservation of the engine, do not have as their primary purpose the inhibition of marine growth (in fact, Pearce still allows sunlight to penetrate the system), and are accordingly, in view of their complexity, much more costly than necessary for this purpose. Their complexity also makes them difficult to install, routinely, onto a stern drive unit. Furthermore, the Pearce and Shaw devices are bulky and accordingly inconvenient to store on board a boat.
Various other types of boat engine covers are known, but are, like the Shaw device, primarily concerned with systems for flushing engines with fresh water. Examples of such covers are disclosed in the following U.S. patents:
______________________________________ U.S. Pat. No. Issue date Inventor ______________________________________ 3,220,374 30 November, 1965 Sloan 3,886,889 3 June, 1975 Burger 4,869,695 26 September, 1989 Sajdak, Jr. 5,072,683 17 December, 1991 Colonna ______________________________________
There remains a significant need for an inexpensive, portable, easily-stored anti-fouling protective cover which can be easily installed onto marine stern drive units using simple tools available to all boaters.